Machining or metalworking fluids are in widespread, high volume use throughout the manufacturing industry for their coolant, lubricant, and corrosion resistant properties during operations such as metal cutting, grinding, boring, drilling, and turning. These fluids are made of complex mixtures of oils, detergents, surfactants, biocides, lubricants, anti-corrosion agents, and other potentially toxic ingredients. While these fluids are essential for metal forming and machining, they are currently being examined with increased scrutiny because of hazards associated with worker exposure, including but not limited to skin rashes, increased cancer rates, respiratory problems and other issues. In fact, there is substantial scientific literature documenting that worker exposure to machining fluids is strongly associated with skin problems, and malignant respiratory effects such as occupational asthma. These fluids also pose substantial environmental problems associated with their disposal. There is now universal agreement on the need for safer more environmentally friendly metalworking fluids.
Various patents disclose additives formulated as lubricating agents into metal-forming and/or machining fluids. Boric acid, alkali borates, and borate esters are conventionally known for their beneficial effects when included in lubricating oil formulations. Polyhydric alcohol and polyalkylene glycol have also been used or added in oils to enhance their properties. The use of alkyl carboxylates, such as the ester glycerol monooleate, have also found uses as beneficial additives or as components in lubricating oil compositions.
Borated lubrication compounds are known lubrication additives for oil and fuel compositions. Borated lubrication compounds are known to have high viscosity indices and favorable low temperature characteristics. Such boron-containing compounds are known to be non-corrosive and to possess antioxidant, fire retarding and potential antifatigue characteristics. Such compounds may also exhibit antiwear and high temperature dropping point properties for greases. Borated esters and hydrocarbonyl vicinal diols have previously been proposed as lubricant additives, especially as mixtures of long chain alcohols or hydroxyl-containing aliphatic, preferably alkyl, carboxylates. Borated lubrication compounds are generally obtained by synthetic methods known in the art. Typically, these borated lubrication compounds are prepared by reacting boric acid or boric oxide with appropriate aliphatic or alkoxylated compounds.
Borated derivatives of phosphorus are also known additives for lubricant compositions. Such borated phosphorus derivatives include borated dihydrocarbonyl phosphonates. Borated phosphite additives may be synthesized by reacting dihydrocarbonyl phosphites with such boron-containing compounds as boric oxide, metaborates, alkylborates or boric acid in the presence of a hydrocarbonyl vicinal diol.
Organometallic boron-containing compounds are yet another class of additives. These compounds contain a metal capable of forming a complex with an organic compound. Useful metals for use in such compounds include Na, K, Mg, Ca, Sr, Ba, Ti, Zr, V, Cr, Ni, Mn, Fe, Co, Cu, Zn, B, Pb, and Sb. Borated versions of such organometallic complexes are derived or synthesized from both aliphatic and heterocyclic organic compounds.
Although various references describe boron-containing additives that provide lubricity to metal-forming or cutting lubricant compositions, conventionally known additives are based on compositions that require complex formulations and lengthy preparation and therefore are not cost effective as lubricants. Also, large amounts of boron additives are needed in order to achieve sufficient lubricity. Some of the lubricant compositions contain organic and/or petroleum based products that are flammable and difficult to clean and/or dispose after the metal-forming or machining operations. Their incorporation into carrier fluids would likely require complex processing steps and hence be prohibitively expensive. A need therefore remains for a readily available product that is cost effective, easy to apply, use and/or dispose.